\section{Conclusion} 
\label{sec:conclusion}

This paper investigates experimentation characteristics and testbed
 usage patterns in five public testbeds. 
We present results from a rigorous systematic empirical 
 analysis of data on node usage,
experiment duration, experiment topology, project
descriptions, membership information, and activity information 
 from these testbed. 
Additionally, we also present results from a traditional user survey of  
 testbed users. 
 
Experimentation has been actively used in the last decade
 for distributed and networking research since it 
assists in the creation and refinement of models that,
 when well constructed, can lead to better analysis and simulations.
However, design and running 
 of valid experiments is very challenging. 
Also the challenges of good experimentation design and execution 
 increase as the scale and duration of the experiment
 increases.

We find that most testbed users experiment at smaller-scales 
 and gradually develop larger-scale experiments  
 to overcome some of these challenges.
We also find that testbed usage is continuously 
 increasing in the research community, 
  but we still lack tools and services 
  to make experiment management easier for the users. 
In addition to building large and more diverse testbeds, 
 testbed-based networking and distributed research
 would greatly benefit from more science to add to 
  the current-state-of-art of unguided experimentation. 
  
  
